Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$110.32	4.541%	$115.3296	$115.33	$115.35	$115.30
Purchase #2	$200.57	11.661%	$223.9585	$223.96	$223.95	$224.00
Purchase #3	$158.95	13.201%	$179.933	$179.93	$179.95	$179.90
Purchase #4	$246.99	5.204%	$259.8434	$259.84	$259.85	$259.80
Purchase #5	$137.25	4.152%	$142.9486	$142.95	$142.95	$142.90
Purchase #6	$182.89	9.612%	$200.4694	$200.47	$200.45	$200.50
Purchase #7	$177.74	4.591%	$185.9	$185.90	$185.90	$185.90
7 purchase totals =	$1,214.71		$1,308.3825	$1,308.38	$1,308.40	$1,308.30